glennf / cedar

Implementation of the Cedar Policy Language

Cedar

This repository contains source code of the Rust crates that implement the Cedar policy language.

Cedar is a language for writing and enforcing authorization policies in your applications. Using Cedar, you can write policies that specify your applications' fine-grained permissions. Your applications then authorize access requests by calling Cedar's authorization engine. Because Cedar policies are separate from application code, they can be independently authored, updated, analyzed, and audited. You can use Cedar's validator to check that Cedar policies are consistent with a declared schema which defines your application's authorization model.

Cedar is:

Expressive

Cedar is a simple yet expressive language that is purpose-built to support authorization use cases for common authorization models such as RBAC and ABAC.

Performant

Cedar is fast and scalable. The policy structure is designed to be indexed for quick retrieval and to support fast and scalable real-time evaluation, with bounded latency.

Analyzable

Cedar is designed for analysis using Automated Reasoning. This enables analyzer tools capable of optimizing your policies and proving that your security model is what you believe it is.

Using Cedar

Cedar can be used in your application by depending on the cedar-policy crate.

Just add cedar-policy as a dependency by running

cargo add cedar-policy

Crates in This Workspace

• cedar-policy : Main crate for using Cedar to authorize access requests in your applications, and validate Cedar policies against a schema
• cedar-policy-cli : Crate containing a simple command-line interface (CLI) for interacting with Cedar
• cedar-policy-core : Internal crate containing the Cedar parser and evaluator
• cedar-policy-validator : Internal crate containing the Cedar validator
• cedar-policy-formatter : Internal crate containing an auto-formatter for Cedar policies
• cedar-integration-tests : Crate containing integration tests

Quick Start

Let's put the policy in policy.cedar and the entities in entities.json.

policy.cedar:

permit (
  principal == User::"alice",
  action == Action::"view",
  resource in Album::"jane_vacation"
);

This policy specifies that alice is allowed to view the photos in the "jane_vacation" album.

entities.json:

[
    {
        "uid": { "type": "User", "id": "alice"} ,
        "attrs": {"age": 18},
        "parents": []
    },
    {
        "uid": { "type": "Photo", "id": "VacationPhoto94.jpg"},
        "attrs": {},
        "parents": [{ "type": "Album", "id": "jane_vacation" }]
    }
]

Cedar represents principals, resources, and actions as entities. An entity has a type (e.g., User) and an id (e.g., alice). They can also have attributes (e.g., User::"alice"'s age attribute is the integer 18).

Now, let's test our policy with the CLI:

 cargo run authorize \
    --policies policy.cedar \
    --entities entities.json \
    --principal 'User::"alice"' \
    --action 'Action::"view"' \
    --resource 'Photo::"VacationPhoto94.jpg"'

CLI output:

ALLOW

This request is allowed because VacationPhoto94.jpg belongs to Album::"jane_vacation", and alice can view photos in Album::"jane_vacation".

If you'd like to see more details on what can be expressed as Cedar policies, see the documentation.

Examples of how to use Cedar in an application are contained in the repository cedar-examples. TinyTodo is a simple task list management app whose users' requests, sent as HTTP messages, are authorized by Cedar. It shows how you can integrate Cedar into your own Rust program.

Documentation

General documentation for Cedar is available at docs.cedarpolicy.com, with source code in the cedar-policy/cedar-docs repository.

Generated documentation for the latest version of the Rust crates can be accessed on docs.rs.

If you're looking to integrate Cedar into a production system, please be sure the read the security best practices

Building

To build, simply run cargo build (or cargo build --release).

What's New

We maintain changelogs for our public-facing crates: cedar-policy and cedar-policy-cli. For a list of the current and past releases, see crates.io or Releases.

Backward Compatibility Considerations

Cedar is written in Rust and you will typically depend on Cedar via Cargo. Cargo makes sane choices for the majority of projects, but your needs may differ. If you don't want automatic updates to Cedar, then you can pin to a specific version in your Cargo.toml. For example:

[dependencies]
cedar-policy = "=2.4.2"

Note that this is different from:

[dependencies]
cedar-policy = "2.4.2"

Which expresses that 2.4.2 is the minimum version of Cedar you accept, and you implicitly accept anything newer that is semver-compatible. See https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html.

Security

See SECURITY for more information.

Contributing

We welcome contributions from the community. Please either file an issue, or see CONTRIBUTING

License

This project is licensed under the Apache-2.0 License.